[turbofan] Add support for loading missing properties.

src/compiler/js-native-context-specialization.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/js-native-context-specialization.h"
 
 #include "src/accessors.h"
 #include "src/code-factory.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-builder.h"
@@ skipping 285 matching lines @@
   }
   effect = graph()->NewNode(
       simplified()->StoreField(AccessBuilder::ForPropertyCellValue()),
       jsgraph()->Constant(property_cell), value, effect, control);
   return Replace(node, value, effect, control);
 }
 
 
 Reduction JSNativeContextSpecialization::ReduceNamedAccess(
     Node* node, Node* value, MapHandleList const& receiver_maps,
-    Handle<Name> name, PropertyAccessMode access_mode) {
+    Handle<Name> name, PropertyAccessMode access_mode,
+    LanguageMode language_mode) {
   DCHECK(node->opcode() == IrOpcode::kJSLoadNamed ||
          node->opcode() == IrOpcode::kJSStoreNamed);
   Node* receiver = NodeProperties::GetValueInput(node, 0);
   Node* frame_state = NodeProperties::GetFrameStateInput(node, 1);
   Node* effect = NodeProperties::GetEffectInput(node);
   Node* control = NodeProperties::GetControlInput(node);
 
   // Not much we can do if deoptimization support is disabled.
   if (!(flags() & kDeoptimizationEnabled)) return NoChange();
 
@@ skipping 75 matching lines @@
                                  this_control_count, &this_controls.front());
     }
 
     // Determine actual holder and perform prototype chain checks.
     Handle<JSObject> holder;
     if (access_info.holder().ToHandle(&holder)) {
       AssumePrototypesStable(receiver_type, holder);
     }
 
     // Generate the actual property access.
-    if (access_info.IsDataConstant()) {
+    if (access_info.IsNotFound()) {
+      DCHECK_EQ(PropertyAccessMode::kLoad, access_mode);
+      if (is_strong(language_mode)) {
+        // TODO(bmeurer/mstarzinger): Add support for lowering inside try
+        // blocks rewiring the IfException edge to a runtime call/throw.
+        exit_controls.push_back(this_control);
+        continue;
+      } else {
+        this_value = jsgraph()->UndefinedConstant();
+      }
+    } else if (access_info.IsDataConstant()) {
       this_value = jsgraph()->Constant(access_info.constant());
       if (access_mode == PropertyAccessMode::kStore) {
         Node* check = graph()->NewNode(
             simplified()->ReferenceEqual(Type::Tagged()), value, this_value);
         Node* branch = graph()->NewNode(common()->Branch(BranchHint::kTrue),
                                         check, this_control);
         exit_controls.push_back(graph()->NewNode(common()->IfFalse(), branch));
         this_control = graph()->NewNode(common()->IfTrue(), branch);
       }
     } else {
@@ skipping 166 matching lines @@
           ? exit_controls.front()
           : graph()->NewNode(common()->Merge(exit_control_count),
                              exit_control_count, &exit_controls.front());
   Node* deoptimize = graph()->NewNode(common()->Deoptimize(), frame_state,
                                       exit_effect, exit_control);
   // TODO(bmeurer): This should be on the AdvancedReducer somehow.
   NodeProperties::MergeControlToEnd(graph(), common(), deoptimize);
 
   // Generate the final merge point for all (polymorphic) branches.
   int const control_count = static_cast<int>(controls.size());
-  if (control_count == 1) {
+  if (control_count == 0) {
+    value = effect = control = jsgraph()->Dead();
+  } else if (control_count == 1) {
     value = values.front();
     effect = effects.front();
     control = controls.front();
   } else {
     control = graph()->NewNode(common()->Merge(control_count), control_count,
                                &controls.front());
     values.push_back(control);
     value = graph()->NewNode(common()->Phi(kMachAnyTagged, control_count),
                              control_count + 1, &values.front());
     effects.push_back(control);
@@ skipping 11 matching lines @@
 
   // Extract receiver maps from the LOAD_IC using the LoadICNexus.
   MapHandleList receiver_maps;
   if (!p.feedback().IsValid()) return NoChange();
   LoadICNexus nexus(p.feedback().vector(), p.feedback().slot());
   if (nexus.ExtractMaps(&receiver_maps) == 0) return NoChange();
   DCHECK_LT(0, receiver_maps.length());
 
   // Try to lower the named access based on the {receiver_maps}.
   return ReduceNamedAccess(node, value, receiver_maps, p.name(),
-                           PropertyAccessMode::kLoad);
+                           PropertyAccessMode::kLoad, p.language_mode());
 }
 
 
 Reduction JSNativeContextSpecialization::ReduceJSStoreNamed(Node* node) {
   DCHECK_EQ(IrOpcode::kJSStoreNamed, node->opcode());
   NamedAccess const& p = NamedAccessOf(node->op());
   Node* const value = NodeProperties::GetValueInput(node, 1);
 
   // Extract receiver maps from the STORE_IC using the StoreICNexus.
   MapHandleList receiver_maps;
   if (!p.feedback().IsValid()) return NoChange();
   StoreICNexus nexus(p.feedback().vector(), p.feedback().slot());
   if (nexus.ExtractMaps(&receiver_maps) == 0) return NoChange();
   DCHECK_LT(0, receiver_maps.length());
 
   // Try to lower the named access based on the {receiver_maps}.
   return ReduceNamedAccess(node, value, receiver_maps, p.name(),
-                           PropertyAccessMode::kStore);
+                           PropertyAccessMode::kStore, p.language_mode());
 }
 
 
 Reduction JSNativeContextSpecialization::Replace(Node* node,
                                                  Handle<Object> value) {
   return Replace(node, jsgraph()->Constant(value));
 }
 
 
 bool JSNativeContextSpecialization::LookupInScriptContextTable(
@@ skipping 71 matching lines @@
 }
 
 
 SimplifiedOperatorBuilder* JSNativeContextSpecialization::simplified() const {
   return jsgraph()->simplified();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8